Serious game crashing problem

Ok I am so frustrated and REALLY DESPERATE. I have had this PC for two years. It has worked fine. I recently reformatted due to a networking problem i couldnt fix and got frustrated... Now after my reinstallation EVERY game I play crashes a few minutes into gameplay. Also during regurlar PC use like Internet browsing my screen will freeze and then flash black when the picture returns everything works fine... except for games of course. Here are my specs:

Now here is the LONG list of things I have already tried.
I reformatted my computer literally a couple of hours after the first reformatt.
I ran all of the DXDiag tests.
I wiped the video drivers and reinstalled using Driver Cleaner Pro.
I updated my sound card drivers
I disabled my on board sound
I ran SpeedFan to monitor my CPU temp it runs between 32-40 degrees C.

I havent messed with the chipset drivers only drivers post windows startup. Do you think there is a problem with my power supply? and I dont think I've made any changes to the Bios I've only accessed the startup menu to boot from cd.

You have to install the chipset drivers for your motherboard. This is probably the reason your system is crashing. I think Windows has some generic/default drivers that it uses just so your system is functional, BUT it is most important to download and install the most current chipset drivers supplied by your motherboard manufacture.

You will need to know the make and model of your motherboard and possibly the board revision too. Go to the manufacture's website and download and install them.

It makes no sense to consider your PSU or any other component until you have done this step. If you need any help with this, post back.

Figure out which one and download/install the updated drivers. OR you can simply download/install Live Update and let that run. It will detect exactly what mobo you have and download and install the appropriate drivers. You will actually pick which drivers to install.